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Re: [PATCH 2/3] block/io: wait for serialising requests when a request b
From: |
Kevin Wolf |
Subject: |
Re: [PATCH 2/3] block/io: wait for serialising requests when a request becomes serialising |
Date: |
Wed, 18 Dec 2019 17:47:34 +0100 |
User-agent: |
Mutt/1.12.1 (2019-06-15) |
Am 18.12.2019 um 14:17 hat Paolo Bonzini geschrieben:
> Marking without waiting would not result in actual serialising behavior.
> Thus, make a call bdrv_mark_request_serialising sufficient for
> serialisation to happen.
>
> Signed-off-by: Paolo Bonzini <address@hidden>
> @@ -1851,13 +1841,18 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t
> offset, uint64_t bytes,
> assert(!(flags & ~BDRV_REQ_MASK));
>
> if (flags & BDRV_REQ_SERIALISING) {
> - bdrv_mark_request_serialising(req, bdrv_get_cluster_size(bs));
> + waited = bdrv_mark_request_serialising(req,
> bdrv_get_cluster_size(bs));
> + /*
> + * For a misaligned request, we should have already waited
> + * in bdrv_padding_rmw_read and locked out concurrent writers.
Actually, bdrv_padding_rmw_read() only asserts that the request is
already serialised. bdrv_mark_request_serialising() is already called by
the callers of bdrv_padding_rmw_read().
> + */
> + assert(!waited ||
> + (req->offset == req->overlap_offset &&
> + req->bytes == req->overlap_bytes));
> + } else {
> + bdrv_wait_serialising_requests(req);
> }
>
> - waited = bdrv_wait_serialising_requests(req);
> -
> - assert(!waited || !req->serialising ||
> - is_request_serialising_and_aligned(req));
> assert(req->overlap_offset <= offset);
> assert(offset + bytes <= req->overlap_offset + req->overlap_bytes);
> assert(end_sector <= bs->total_sectors || child->perm & BLK_PERM_RESIZE);
Other than the comment, the patch looks fine to me.
Kevin
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